Technical Abstract:
Two very different strategies have been proposed as tools to assess the potential invasiveness of non-native woody plants. The first, developed by Reichard and Hamilton, is based primarily on life-history characteristics of candidate species and information about their invasiveness and that of related taxa in other parts of the world. This "biological" strategy is designed to operate on a continental scale. The second strategy, developed by Widrlechner and Iles, is based on comparisons of the native distributions of non-native woody plant species that are known to have naturalized with those that have no history of naturalization. These comparisons have been made only on the state level (for Iowa) and have been related to environmental conditions in other parts of the world that are biologically analogous to those in Iowa. This "native distribution" strategy is designed to operate best on a local or regional scale. One of its major limitations is that it does not account for variation in life-history and other biological characteristics associated with potential invasiveness. In this study, we integrate the two strategies by first classifying species under the "biological" strategy. The native ranges of plants that were misclassified with respect to their current status in Iowa were then subjected to geographic and environmental analyses interpreted based on past findings from the "native distribution" strategy. Results from those analyses were then used to create a new, more comprehensive strategy that builds on the strengths of both earlier approaches and has greater predictive power. Information needed to apply this strategy to regions beyond Iowa will also be discussed.